"Interstellar Signal from the 70s Continues to Puzzle Researchers"

                                        By Seth Shostak
                                        SETI Institute
                                        posted: 07:00 am ET
                                        05 December 2002

Of the many "maybes" that SETI has turned up in its four-decade history,
none is better known than the one that was discovered in August, 1977, in
Columbus, Ohio. The famous Wow signal was found as part of a long-running
sky survey conducted with Ohio State University's "Big Ear" radio
telescope. The Wow signal's unusual nomenclature connotes both the
surprise of the discovery and its sox-knocking strength (60 Janskys in a
10 KHz channel, which is more than 50 thousand times more incoming energy
than the minimum signal that would register as a hit for today's Project
Phoenix.  Of special interest is the manner in which it rose and fell over
the course of 72 seconds. Why is this interesting? Just this: the Ohio
State survey kept the telescope fixed, letting the Earth's daily spin
rotate the heavens through its narrow beam. The "beam," of course, was the
elongated patch of sky to which the telescope was sensitive: the direction
from which it could pick up cosmic signals. The sensitivity was greatest
at the center of the beam, falling off to either side. So as a celestial
radio source passed by, it first rose in apparent intensity as Earth's
rotation brought it into the beam, reached a peak in the beam center, and
then faded away. Given the size of the Ohio State beam, this rise and fall
should take 72 seconds. And for the Wow signal, it did.


On the other hand, there are some aspects of this seductive signal that
nudge it toward a lower grade. The Ohio State telescope actually used 
two beams, situated side-by-side on the sky. Any cosmic source would  
therefore be seen first in one (for 72 seconds) and then roughly 3 min
later in the other (also 72 seconds.) The Wow signal failed this simple
test. It came on gangbusters in one beam, but was a no-show in the other:
suspicious and disheartening. But as Gray and others have realized, this
odd, one-beam behavior could be caused by an alien transmission that
simply went off the air during the 3 minutes between beams. Maybe ET went
on vacation, or took an extended lunch break. If the putative aliens
permanently shut down their transmitter, then there's no chance of ever
hearing the Wow signal again. Like a single sighting of the Loch Ness
monster, we would never be able to prove what it was. But if the signal
is periodic if, for example, the aliens are using a rotating radio beacon
that sweeps the star-studded strata of the Milky Way once every five
minutes or every five hours, then we could hope to find it by just
looking again.


In the October 20 issue of The Astrophysical Journal, Gray and Simon
Ellingsen, of Australia's University of Tasmania, report on new 
observations (partially supported by the SETI Institute) designed to test
this idea. Their new try was made at the 26-meter radio telescope in 
Hobart, Tasmania. This southern hemisphere instrument could continuously
follow for most of a day the patch of sky (in the constellation of
Sagittarius) where the "Big Ear" was pointing when it found the "Wow"
signal. They made six 14-hour observations, and even though their 
telescope was rather smaller than the venerable Ohio State antenna, they
still had sufficient sensitivity to find signals only 5% as strong as
Wow's 1977 intensity. They also covered five times as much of the radio
dial as the original "Big Ear" telescope.


Bottom line? No dice. To quote from their article, "no signals resembling
the Ohio State Wow were detected." Of course, if the signal's repetition
cycle were much longer than 14 hours, then even this careful experiment
could have easily missed it. But as Gray and Ellingsen point out, if the
signal were really this infrequent, then the chance to have found it in
the first place was very slim.


So was the Wow signal our first detection of extraterrestrials? It might
have been, but no scientist would make such a claim. Scientific
experiment is inherently, and rightly, skeptical. This isn't just a sour
attitude; it's the only way to avoid routinely fooling yourself. So
until and unless the cosmic beep measured in Ohio is found again, the Wow
signal will remain a "What signal".



Credits: http://www.space.com/searchforlife/seti_shostak_wow_021205.html